Marin water officials unfazed by downgraded El Ni?o predictions

A powerful El Ni?o that had been emerging in the Pacific Ocean is fizzling out — evaporating hopes it will deliver a knockout punch to California's three-year drought — but Marin officials say they aren't worried.

A new report from scientists at the National Oceanic and Atmospheric Administration decreases the probability of an El Ni?o — the condition that occurs when warm Pacific Ocean water at the equator affects the jet stream — to 65 percent starting in October, down from 82 percent in June.

More significantly, researchers said, the ocean water that had been warming steadily through the spring has cooled off in recent months. Most of the world's leading meteorological organizations now say that if an El Ni?o arrives this winter, it is likely to be a weak or moderate one — not the kind historically linked with wetter-than-normal winters in California.

"It's fair to say that it's plateaued," said Michelle L'Heureux, a meteorologist with the NOAA Climate Prediction Center in College Park, Maryland.

Normal rainfall

Water officials in Marin County said they were not concerned by the development, since reservoir levels remain safe and El Ni?o weather patterns don't always assure heavy rains in the winter.

"First of all, it's early. It's August," said Chris DeGabriele, general manager of the North Marin Water District. "Secondly, it's not always a great predictor of a really wet year or a really dry year, especially here in the Bay Area."

Even without a strong El Ni?o winter, Marin Municipal Water District engineer John Lehaye said it won't take an extraordinary rainy season to replenish Marin's water supply.

Because of the rain-gathering prowess of Mount Tamalpais, which helps collect water for the county's more southern reservoirs, Marin Municipal's water supply is at a safer level than North Marin's.

Marin Municipal's reservoirs are 70 percent of capacity, compared to an average of 77 percent at this time of year, said Marin Municipal spokeswoman Libby Pischel.

"It's below average, so it's on the lower side, but it's not extremely low," Pischel said. "There are parts of California that have much more serious issues."

Conservation working

North Marin's Lake Stafford is at 36 percent capacity. But more concerning are the low levels of North Marin's biggest water suppliers, the lakes along the Russian River. Lake Mendocino is at 34 percent capacity, while Lake Sonoma is at 66 percent capacity — which DeGabriele said is "ample water," but is at its lowest level in 25 years.

Both of Marin's water agencies said customers have responded well to voluntary cutbacks.

In Marin Municipal's territory, many water users are abiding by the suggested 25 percent reduction.

"Our customers are doing a good job conserving," Pischel said. "Consumption is down from last year, so we're happy to see that."

Water use in Novato, which is served by the North Marin district, dropped 21 percent from February to July — more than the 20 percent voluntary reduction suggested by the district.

North Marin's customers in West Marin, where a mandatory 25 percent reduction was implemented July 1, had only gone down 7.5 percent since February, officials said.

California could still have a wet winter to help fill depleted reservoirs, replenish streams and raise over-pumped water tables.

If a steady series of low-pressure systems develops off the Pacific coast later in the year, that could bring tropical storms dumping rain in large amounts. The trend, known as an "atmospheric river" or "Pineapple Express," has soaked the state in the past. But it has been all but shut down over the past three years as unusually persistent ridges of high pressure off the coast pushed winter storms north to Canada instead.

But the possibility that a strong El Ni?o won't be there to help is "not good news, especially if we are using El Ni?o as an optimism index. It's not what we want to see," said meteorologist Jan Null, with Golden Gate Weather Services in Saratoga.

"It's like in poker," he added. "If you have one fewer spade out there, the odds of getting that flush are less."

Ocean water

Generally speaking, the warmer the ocean water during El Ni?o years, the greater the likelihood of heavy winter rainfall. During mild El Ni?o years, when the ocean water is only slightly warmer than historic averages, there are just as many drier-than-average winters in California as soaking ones.

Since 1951, there have been six winters with strong El Ni?o conditions. In four of them, rainfall from the Bay Area to Bakersfield was at least 140 percent of the historic average, Null found.

But in the 16 winters since 1951 when there was a weak or moderate El Ni?o, California experienced below-normal rainfall in six of them. There was average rainfall in five and above-normal precipitation in the other five.

Thursday's NOAA report was based on ocean temperature readings from dozens of buoys, wind measurements, satellite images and more than a dozen computer models from scientific agencies around the world.

The last strong El Ni?o event, in the winter of 1997-98, saw Pacific surface temperatures 5 degrees warmer than normal at some times. That led to drenching rainfall across California, landslides that closed Highway 1 in Big Sur and 35 counties being declared disaster areas.